Hereditary nephritis (Alport syndrome) is a genetic disorder in which kidney function is poor, blood is present in the urine, and deafness and eye abnormalities sometimes occur.

Hereditary nephritis is usually caused by a defective gene on the X chromosome, but it sometimes results from an abnormal gene on a nonsex (autosomal) chromosome. Other factors influence how severe the disorder is in a person who has the defective gene. Hereditary nephritis can cause chronic kidney disease, sometimes with loss of most kidney function (kidney failure).

Females with the defective gene on one of their two X chromosomes usually do not have symptoms, although their kidneys may function somewhat less efficiently than normal. Most of these females have some blood in the urine. Occasionally, a female loses most kidney function (kidney failure). Males with the defective gene on their one X chromosome develop more severe problems because males do not have a second X chromosome to compensate for the defect. Males usually develop kidney failure between the ages of 20 and 30, but in some males, the defective gene does not cause kidney failure until ages 40 to 50.

Many people with the defective gene on only one autosomal chromosome have no symptoms other than blood in the urine, but the urine may also contain varying amounts of protein, white blood cells, and casts (clumps of blood cells) that are visible under a microscope. Kidney function in people who have the defective gene on two autosomal chromosomes slowly worsens, and kidney failure usually occurs.

Hereditary nephritis can affect other organs. Hearing problems, usually an inability to hear sounds in the higher frequencies, are common. Cataracts can also occur, although less often than hearing loss. Abnormalities of the corneas, lenses, or retina sometimes cause blindness. Other problems include a low number of platelets in the blood (thrombocytopenia) and abnormalities that affect several nerves (polyneuropathy).

People who develop kidney failure need to undergo dialysis or receive a kidney transplant. Genetic testing is usually offered to people who want to have children.

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